The existing $data is a reference to an array containing an array hashes, and the data you are adding are arrays being added to the top-level array. This is why your data structure looks odd (see below).

Data, as presented: 

$data = \[
            [
              'City Name',
              'Last Name',
              'First Name',
              'Address'
            ],
            [
              '',
              '',
              '',
              ''
            ],
            [
              {
                'FIRST_NAME' => 'John',
                'CITY' => 'San Frans',
                'LAST_NAME' => 'Doe',
                'ADDRESS' => '100 Main St.'
              }
            ]
          ];

[download]

If you change the assignment in _test to the form my @data = ( ... );, I believe it will appear more as you expect. (It does, however, mean that the elements of the array differ in type.)

Data, after suggested change: 

$data = \[
            [
              'City Name',
              'Last Name',
              'First Name',
              'Address'
            ],
            [
              '',
              '',
              '',
              ''
            ],
            {
              'FIRST_NAME' => 'John',
              'CITY' => 'San Frans',
              'LAST_NAME' => 'Doe',
              'ADDRESS' => '100 Main St.'
            }
          ];

[download]

Hope that helps.

Update: 2014-12-02

Based on that premise, then, changing the unshift() line in your code to unshift @{ $data }[0], @{ $header_row }; appears to have your desired effect (see below).

Data, after change suggestion 2: 

$data = \[
            [
              [
                'City Name',
                'Last Name',
                'First Name',
                'Address'
              ],
              [
                '',
                '',
                '',
                ''
              ],
              {
                'FIRST_NAME' => 'John',
                'CITY' => 'San Frans',
                'LAST_NAME' => 'Doe',
                'ADDRESS' => '100 Main St.'
              }
            ]
          ];

[download]

In reply to Re: Adding rows of data by atcroft
in thread Adding rows of data by Anonymous Monk

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